The thickness of a wafer has become thinner over the course of semiconductor development, going from a thickness of 625 micrometers (μm) down to a thickness as low as 100 μm.
A conventional wafer shipping box includes a base, a cover, an lower pad that is connected to the base, an upper pad that is connected to the cover, and a wafer cassette. The wafer cassette has a plurality of confining slots that are spaced apart from each other for holding wafers, each of which is further confined from movement by the upper and lower pads. As the structure and size of each of the elements of the wafer shipping box are required to be compatible with various conventional automation equipment, the width of each of the confining slots of the wafer cassette is also required to correspond to thickness of a standard-sized wafer. However, with advanced design of the thinner wafer, the width of each of the confining slots has become too large to properly hold this type of wafer securely, possibly leaving much larger gap that may easily cause the wafer to misalign and to be prone to exterior damage.
To address the abovementioned issues, each of the upper and lower pads is designed to be formed with a plurality of V-shaped grooves, each of which is adapted to receive a corresponding one of the wafers and to restrict movement of the corresponding one of the wafers through confinement of upper and lower edges thereof. However, when the cover of the conventional wafer shipping box is removed, the thinner wafers would still lean toward and collide with either sides of their respective confining slots which are wide relative to the thickness of the thinner wafers, possibly become attached to neighboring wafers to make retrieval and placement of the wafers difficult. In the most severe scenario, the wafers may be damaged or break apart.